Untersuchung zum Einfluss verschiedener Bisphosphonate auf Zellviabilität und Migrationsfähigkeit von Osteoblastem, Fibroblasten, HUVEC und EPC sowie ihrer Beeinflussung durch Geranyl-Geraniol Substitution

Bisphosphonates are osteoanabolic drugs commonly used in the treatment of bone disseases including malignant bone neoplasia, bone metastasis, muliple myeloma, Paget´s dissease or osteoprosis. Despite their therapeutical properties one main side effect is the development of osteonecrosis of the jaw (BP-ONJ). The pathogenesis of BP-ONJ remains unclear, however it is assumed to be mulitfactoriell. Although the main mechanism of action of bisphosphonates is the inhibition of osteoclasts leading to a reduced bony remodelling, extra-sceletall effects of bisphonsphonates have been published throughout literatur. Regarding the generations of the bisphosphonate there are two different molecular mechanisms of action. While first generation bisphosphates like Clodronate induced their effect by incooperation in an ATP-analoga, recent bisphosphonat generations inhibit enzymes in the mevalonat pathway. This leads to a reduced activation of small GTP-binding proteins. The following cellular signaling-pathways are impaired. The aim of this study was to analyse the impact of four bisphosphonates (Clodronat, Pamidronat, Ibandronat and Zoledronat) on four different celllines (Osteoblasts, Fibroblasts, Endothelial Progenitor Cells and Endothel Cells of the human umbilical cord). Furthermore the influence of geranyl-geraniol substitution should be investigated. The data of the present study revealed a significant depressing effect of all four bisphosphonates on the migration ability of fibroblasts, endothelial progenitor cells and osteoblasts. The nitrogen containing bisphosphonates (pamidronate, ibandronate and zoledronate) had furthermore a significant inhibitory impact on HUVEC. The results of the MTT assay demonstrated a decreased cellviability of HUVEC of all four bisphosphonates in a 50μM concentration. The bisphosphonates with increased biological potency (zoledronat, ibandronat) revealed even an inhibitory effect of cellviability in 5μM concentration. The cellviability of fibroblast was decreased in the MTT assay in 50μM concentration of clodronate, ibandronate and zoledronate. All four bisohosphonates showed a depressing effect on endothelial progenitor cells typical characteristic of colony forming even in a 5μM concentration. Geranyl-Geraniol substitution demonstrated an attenute impact on bisphosphonate effect on all four cell lines. The migration ability of cells of angiogenesis (EPC and HUVEC) was significantly elevated with geranyl-geraniol subsitution of allbisphosphonates. Geranyl-geraniol substitution led to a significantly improved migration ability of fibroblasts when added to the bisphosphonates clodronate, pamidronate and ibandronate. Also a significant increase of migration after geranylgeraniol substitution could be observed in osteoblasts when pretreated with ibandronate. The tests on the viability showed an improvement after geranyl-geraniol subsitution. The viability of fibroblasts could be significantly increased after geranyl-geraniol susbstitution when pretreatment with ibandronate in 50μM or 5μM and zoledronate 50μM concentration had been performed. In HUVEC a significantly enhanced viability could be observed after geranyl-geraniol subsitution in the 50μM clodronate and 5 and 50μM zoledronate group. The impact on the typical characteristic of EPC the colony forming property could be significantly improved after geranyl geraniol subsitution within all four bisphosphonate groups regardsless of the tested concentrations (5, 25 and 50μM). Bisphosphonates have an inhibtory effect on the migration ability of all tested cells. Furthermore they highly influence the cell-viability. Both characterics can be weaked by the subsitution of geranyl-geraniol. These in vitro findings are a promising approach for further testing in an in vivo model as a potential local therapeutical agency against bisphosphonate related osteonecrosis of the jaw.